Resumen

In lymphocytes, Fas activation leads to both apoptosis and necrosis, whereby the latter form of cell death is linked to delayed production of
endogenous ceramide and is mimicked by exogenous administration of long- and short-chain ceramides. Here molecular events associated with
noncanonical necrotic cell death downstream of ceramide were investigated in A20 B lymphoma and Jurkat T cells. Cell-permeable, C6-ceramide
(C6), but not dihydro-C6-ceramide (DH-C6), induced necrosis in a time- and dose-dependent fashion. Rapid formation of reactive oxygen species
(ROS) within 30 min of C6 addition detected by a dihydrorhodamine fluorescence assay, as well as by electron spin resonance, was accompanied
by loss of mitochondrial membrane potential. The presence of N-acetylcysteine or ROS scavengers like Tiron, but not Trolox, attenuated
ceramide-induced necrosis. Alternatively, adenovirus-mediated expression of catalase in A20 cells also attenuated cell necrosis but not apoptosis.
Necrotic cell death observed following C6 exposure was associated with a pronounced decrease in ATP levels and Tiron significantly delayed ATP
depletion in both A20 and Jurkat cells. Thus, apoptotic and necrotic death induced by ceramide in lymphocytes occurs via distinct mechanisms.
Furthermore, ceramide-induced necrotic cell death is linked here to loss of mitochondrial membrane potential, production of ROS, and
intracellular ATP depletion.